Figure of speech in poet's last line (5)
I believe the answer is:
trope
'figure of speech' is the definition.
(I've seen this before)
'poet's last line' is the wordplay.
'last' indicates one should take the final letters.
'line' becomes 'rope' (rope is a kind of line**).
The final letter of 'poet' is 't'.
't'+'rope'='TROPE'
'in' acts as a link.
(Other definitions for trope that I've seen before include "metaphor, perhaps" , "ironical expression" , "Figurative use of a word, metaphor" , "figuratively speaking" , "literary effect" .)